The analysis of UWB SiGe HBT LNA for its noise, linearity, and minimum group delay variation

The design of ultra-wideband (UWB) low-noise amplifiers (LNAs) require additional circuit design principles, which differ from those used in conventional LNAs. The design of a low-dc-power-consumption SiGe HBT LNA covering the 2-10-GHz range is demonstrated for UWB applications. Important design factors that must be carefully considered for UWB applications are analyzed, which include power dissipation, operating bandwidth, noise figure, group delay variation, and linearity. The dominant factor for low group delay variation in UWB LNAs is identified through the theoretical analysis. The linearity behavior over the wide bandwidth is analyzed and explained using the Volterra series. Second-harmonic cancellation is determined to be the dominant degradation factor for linearity. The implemented SiGe LNA achieves a gain of 13 dB, a minimum noise figure of 3.3 dB, and an input third-order intercept point of -7.5 dBm between 2-10 GHz while consuming a dc power of only 9.6 mW. This SiGe UWB LNA exhibits less than 22 ps of uniform group delay variation over the entire band.